Ginseng is known as an adaptogenic herb and has been taken orally as an adaptogen for many purposes, inter alia, for the prolongation of life. Traditionally, ginseng is used to enhance body functions against stress, fatigue, diseases, cancer and diabetes. Such a pharmaceutical belief has led people for hundreds of years in Korea, China and Japan to ingest ginseng. Currently, ginseng is one of the most famous and precious herbal medicines consumed around the world (Tyler, J. Pharm. Technol. 11, 214-220, 1995).
Ginsenosides the presence of which characterizes ginseng have typically been utilized in many physiological and pharmaceutical studies since they were first isolated and characterized in the early 1960s (Shibata, et al., Tetraheadron Letters No. 10, pp. 419-422, 1962). In addition, ginseng was also found to contain other ingredients including polysaccharides, polyacetylenes, and proteins (Nah, Kor. J. Ginseng Sci. 21, 1-12, 1997).
Ginsenosides are present in a small amount in ginseng and can be obtained by means of complicated isolation processes. Pure ginsenosides are highly expensive. For these reasons, a crude ginseng total saponin fraction (CGSF), which is obtained from ginseng roots by a butanol extraction method, is mostly employed for studies (Kanzaki, et al. Br J Pharmacol. 125(2), 255-262, 1998; Choi, et al. Br J. Pharmacol. 132, 641-648, 2001; Choi, et al., J. Biol. Chem. 276, 48797-48802, 2001; Choi, et al. Eur J Pharmacol 468, 83-92, 2003; Lee, et al, J Biol Chem. 279, 9912-9921, 2004; Jeong, et al, Br J Pharmacol. 142, 585-593, 2004; Reay, et al, J Psychopharmacol. 19, 357-365, 2005; Lee, et al, Arch Pharm Res 28, 413-420, 2005; Wei, et al J Ethnopharmacol. 111, 613-618, 2007; Eriksson, et al J Ethnopharmacol. 119, 17-23, 2008).
CGSF is found to take advantage of membrane signaling pathways when exerting its ginsenosidic activity. For example, Choi et al. demonstrated that ginsenoside treatment increased Ca2+-activated chloride channel (CaCC) current through the signaling pathway that activates PTX-insensitive Gαq/11 proteins coupled to PLCβ-IP3 in Xenopus oocytes (Choi, et al., J. Biol. Chem. 276, 48797-48802, 1 2001). Further, Lee et al. reported that CaCC currents produced by ginsenoside treatment diminished spontaneously after reaching peak amplitudes even in the continued presence of CGSF in Xenopus oocytes (Lee, et al, J Biol Chem. 279, 9912-9921, 2004).
Intraoocyte injection of calmodulin or depletion of intracellular calcium reservoirs inhibited CGSF-induced Ca2+-activated CI-current activation (Lee, et al, Arch Pharm Res 28, 413-420, 2005). Further, studies revealed that CGSF treatment induced SOCE (stored-operated Ca2+ entry) in Xenopus oocytes (Jeong, et al, Br J Pharmacol. 142, 585-593, 2004), which caused an increase in extracellular or intracellular calcium level, allowing for the activation of CaCC in the Xenopus oocytes (Dascal, CRC Crit Rev Biochem 22, 317-387, 1987).
Surprisingly, the present inventors found that in the course of purifying ginsenosides from CGSF in order to confirm ginsenoside-induced CaCC activation, the induction of CGSF rapidly disappeared or was not obtained upon treatment with fractions which were more abundant in ginsenoside compared to CGSF, that is, ginsenosides purified from CGSF lacking the ability to induce CaCC activation in Xenopus oocyte, suggesting the presence of an unknown substance in CGSF, which has a major influence on CaCC activation in Xenopus oocytes.
Based on the finding, intensive and through research was made to isolate and identify the bioactive substance, culminating in the present invention.